Stephan Maximilian Herbert Röhrl

• Høgevold, Magnus; Hansen, M. M.; Brattgjerd, Jan Egil & Röhrl, Stephan Maximilian Herbert (2026). Interlocking plate compared with conventional pin fxation for undisplaced femoral neck fractures: a randomized controlled trial with radiostereometric analysis. Bone & Joint Open (BJO). 7(9), p. 1154–1162. doi: 10.1302/2633-1462.79.BJO-2026-0008.R1. Full text in Research Archive
• Acke, Manou; Keelson, Benyameen; Engseth, Lars; Øhrn, Frank-David; Gompel, Gert Van & Röhrl, Stephan Maximilian Herbert [Show all 9 contributors for this article] (2026). Precision of an automated surface-based CT-RSA (asCTRSA) for assessing tibial implant migration: a porcine cadaver study and a clinical case. Acta Orthopaedica. ISSN 1745-3674. 97, p. 484–490. doi: 10.2340/17453674.2026.46156. Full text in Research Archive Show summary

  Background and purpose: Radiostereometric analysis (RSA) is the reference standard for migration analysis, but adoption is limited by invasive marker implantation and specialized equipment. We developed an automated, surface-based CT-RSA (asCTRSA) method that reports a registration quality measure (mean rigid-body fitting error, ME). Our aim was to evaluate the precision by comparing asCTRSA with marker-based RSA and CT-based Micromotion Analysis (CTMA, v25.1). Methods: Precision was assessed in a retrospective, repeated-measures, zero-migration study using a porcine cadaver tibial implant scanned in 7 positions (21 double examinations). Migration was reported as maximum total point motion (MTPM) for RSA and asCTRSA. CTMA provided maximum total translation (mTT) as an estimate of MTPM. Mean rigid-body fitting error (ME) was calculated for RSA and asCTRSA (acceptability threshold 0.35 mm). The minimal important difference for MTPM/mTT was 0.1 mm. asCTRSA was applied to 1 clinical case with known migration 3 and 8 months postoperatively (NCT04017533). Results: In the porcine study, precision was 0.09 mm (95% confidence interval [CI] 0.02–0.18) for asCTRSA, 0.08 mm (CI 0.03–0.12) for CTMA, and 0.45 mm (CI 0.20–0.69) for RSA. In the clinical case, asCTRSA detected increasing migration (MTPM 2.5–3.6 mm) and exceeded CTMA’s mTT by 0.4 mm at 8 months. Mean rigid-body fitting error remained below 0.35 mm. Conclusion: We showed that asCTRSA enables automated, surface-based CT-RSA and demonstrated higher precision than RSA in this zero-migration cadaver setting.

• Bru, Fredrik; Engseth, Lars; Pripp, Are Hugo; Schulz, Anselm; Aae, Tommy Frøseth & Husby, Vigdis Kvitland Schnell [Show all 9 contributors for this article] (2026). Dose reduction does not impact precision of CT-RSA in tibial components in total knee arthroplasty: a randomized controlled trial. Journal of Orthopaedic Surgery and Research. doi: 10.1186/s13018-026-06801-8. Full text in Research Archive Show summary

  Purpose Radiostereometric analysis (RSA) has been the gold standard for implant migration analysis for decades. Our group previously demonstrated in a porcine cadaver model that CT-RSA precision was non-inferior by dose reduction. The aim of this study was to investigate whether this finding applied in a clinical setting. Methods This study is part of the ClessTKA trial comparing a novel 3D printed uncemented medially stabilized total knee arthroplasty (TKA) with Tritanium TKA. Fifty patients were recruited (GMK Sphere n = 26, Tritanium n = 24). All surgeries were performed with mechanical alignment between January and June 2023. CT acquisitions were performed postoperatively within 2 days (standard dose 0.05 mSv, n = 49) and at 1 year (low dose 0.01 mSv, n = 47) using a GE Revolution scanner. CT-RSA analyses of tibial components were performed with Sectra CTMA software by a certified assessor. The primary endpoint was difference in precision (mean) of maximum total point motion (MTPM) between dose levels, with an equivalence interval of 0–0.1 mm. Results Mean difference (95% CI) in MTPM under zero motion circumstances between standard and low dose was 0.007 mm (− 0.018 to 0.032). No clinically meaningful differences were found for migration or rotations. Centre-of-mass analysis showed one significant but clinically irrelevant posterior translation (0.013 mm). Conclusion The findings confirm that reducing the effective radiation dose from 0.05 mSv to 0.01 mSv does not compromise the precision of CT-RSA for tibial components in TKA. The results further support the use of low-dose CT-RSA protocols in clinical studies, enabling substantial reduction in patient radiation exposure without loss of precision. Trial registration Clinicaltrials.gov identifier NCT05651009. Initial release of the study was November 23, 2022. At that time, the software CTMA (Sectra) did not provide the very important Maximum Total Point Motion (MTPM), this was introduced in a later update of the CTMA. Hence there was change in the original protocol retrospectively.

• Hansen, Vinjar Brenna; Schulz, Anselm; Hellum, Christian & Röhrl, Stephan Maximilian Herbert (2026). Movement of the sacroiliac joint during a modified active straight leg raise measured with CT-RSA: a feasibility study. Acta Orthopaedica. ISSN 1745-3674. 97, p. 151–155. doi: 10.2340/17453674.2026.45479. Full text in Research Archive
• Poulsen, Magnus; Röhrl, Stephan Maximilian Herbert; Schulz, Anselm & Stødle, Are Haukåen (2025). Prospective Validation of a Weightbearing CT Stability Threshold for Subtle Lisfranc Injuries. Foot & ankle international. ISSN 1071-1007. 46(12), p. 1386–1394. doi: 10.1177/10711007251374674. Full text in Research Archive Show summary

  Background: Accurate evaluation can be challenging in subtle Lisfranc injuries. Although weightbearing computed tomography (WBCT) provides 3-dimensional assessment under physiological load, its role in diagnosing subtle Lisfranc instability and guiding treatment thresholds remains undefined. Currently there is no consensus on the optimal timing, measurement protocol, or stability threshold with WBCT. Methods: We prospectively recruited patients with nondisplaced (<2 mm), intra-articular fractures and/or avulsion fractures in the tarsometatarsal 1-3 area. To assess Lisfranc joint stability, patients underwent bilateral, single-leg WBCT scans. Medial cuneiform (C1) and second metatarsal (M2) measurements, evaluating the integrity of both the dorsal and interosseous Lisfranc ligament, were combined and compared to the contralateral, healthy side to create a difference score. Threshold of instability was defined as >3 mm C1-M2 difference score. Measurements were tested for agreement using the intraclass correlation coefficient (ICC). Results: 38 patients were included in the study and were able to fully weightbear after a median of 9 days postinjury. Eight patients (21%) had a C1-M2 difference score >3 mm (95% CI, 3.8-5.8) while loading. Instability was confirmed in all 8 patients during a fluoroscopic stress test. The remaining 30 patients, with a C1-M2 difference score <3 mm (95% CI, 0.6-1.1), were classified as stable and received conservative treatment. These patients were followed up with an additional WBCT scan after 12 weeks, and none had signs of Lisfranc instability with a median different score 0.6 mm (95% CI, 0.4-0.7). Our measurement method demonstrated excellent interrater (ICC 0.95, 95% CI, 0.93-0.96) and intrarater agreement (ICC 0.97, 95% CI, 0.96-0.98). Conclusion: For subtle Lisfranc injuries, adequate WBCT can be performed 9 days postinjury. In our study population, using our dual-measuring method, a C1-M2 difference >3 mm on WBCT reliably identified subtle Lisfranc instability.

• Hansen, Michaela Manalili; Ballo, Mohammad Laith & Röhrl, Stephan Maximilian Herbert (2025). Radiostereometric analysis for evaluating inducible fracture micromotion: a scoping review. Acta Orthopaedica. ISSN 1745-3674. 96, p. 822–827. doi: 10.2340/17453674.2025.44897. Full text in Research Archive
• Øhrn, Frank-David; Engseth, Lars; Pripp, Are Hugo; Aae, Tommy Frøseth; Schulz, Anselm & Husby, Otto Schnell [Show all 7 contributors for this article] (2025). Computed tomography-based radiostereometric analysis achieves sufficient precision for femoral implants in total knee arthroplasty: a randomized controlled trial. Journal of Orthopaedic Surgery and Research. 20(1). doi: 10.1186/s13018-025-06517-1. Full text in Research Archive Show summary

  Background Conventional radiostereometric analysis (RSA) has been used for several decades to assess implant migration in total knee arthroplasty (TKA). More recently, computed tomography–based radiostereometric analysis (CT-RSA) has been introduced as an alternative. Experimental studies have demonstrated acceptable precision for CT-RSA; however, this has not yet been validated in a clinical setting. With the emergence of new alignment philosophies in TKA, migration analysis of femoral components has become increasingly important. A key criticism of CT-RSA has been the higher radiation doses compared with conventional RSA, particularly in longitudinal studies involving repeated CT scans. In this study, we evaluated the precision of CT-RSA for assessing femoral component migration in two TKA designs at two different radiation dose levels. We hypothesized that there would be no clinically relevant difference in precision between the two radiation dose levels. Methods We performed a randomized controlled trial of 50 patients using Tritanium and GMK Sphere 3D Metal implants and analysed the precision of the method through double examinations expressed as means with 95% confidence intervals at standard and low-dose levels. The main outcome variable was the difference in mean maximum total point motion. We set the clinical meaningful difference to be more than 0.1 mm based on existing literature. Secondary outcome variables were the means and standard deviations of the translation and rotation of the implants. Findings We found a precision of (mean, standard deviation) 0.20 (0.08) and 0.17 mm (0.06) for standard and low dose respectively, giving a difference (95% confidence interval) of − 0.03 mm (− 0.06–0.00). P-value was 0.031. Variability ratios were 0.009 for the standard deviation test. Interpretation In this first clinical study to assess the precision of computed tomography–based radiostereometric analysis for femoral implants in total knee arthroplasty, we found no clinically relevant difference in precision. Our findings confirm that CT-RSA provides sufficient precision in a clinical setting to enable migration analysis of femoral implants in total knee arthroplasty, even when using very low radiation doses.

• Thoen, Peder Svenkerud; Lindalen, Einar; Nordsletten, Lars & Röhrl, Stephan Maximilian Herbert (2025). Low wear with vitamin E-infused highly cross-linked polyethylene. The Bone & Joint Journal. ISSN 2049-4394. 107 B(11), p. 1182–1188. doi: 10.1302/0301-620X.107B11.BJJ-2025-0273.R1. Full text in Research Archive
• BONDT, Maaike R. DE; Øhrn, Frank-David; Engseth, Lars; Schulz, Anselm; Kaptein, Bart L. & Röhrl, Stephan Maximilian Herbert [Show all 7 contributors for this article] (2025). Precision evaluation of 2 CT-based radiostereometric analysis systems in a cadaver study. Acta Orthopaedica. ISSN 1745-3674. 96, p. 867–872. doi: 10.2340/17453674.2025.44949. Full text in Research Archive Show summary

  Background and purpose: To address the limitations of radiostereometric imaging and to eliminate the need for intraoperative marker placement, CT-based radiostereometric analysis (CT-RSA) software systems have been developed. We aimed to evaluate the precision of a novel CT-RSA software system, V3MA, against an established CT-RSA software system, CTMA, while also examining the impact of CT scanner model on precision. Methods: 7 CT scans per scanner (Siemens SOMATOM Force and GE Revolution) of a porcine cadaver with a knee implant were used for pairwise comparisons. By aligning paired CT scans, the translation (mm), rotation (°), and maximum total point motion (MTPM, mm) of the tibial implant with respect to the bone were computed. V3MA aligned the scans using the voxel gray values of the bone and implant, whereas CTMA aligned the surface points of the bone and implant. The precision of both software systems and the effect of both scanner models were investigated using paired data in a linear mixed model. Results: Both software systems resulted in a similar MTPM (contrast V3MA–CTMA –0.002 mm, 95% confidence interval [CI] –0.015 to 0.011; V3MA: 0.09 mm; CTMA: 0.10 mm), indicating comparable precision using a minimal important difference of 0.10 mm. Using Siemens scanner data resulted in a higher estimated MTPM than using GE scanner data (contrast Siemens–GE 0.046 mm, CI 0.024–0.067; Siemens: 0.12 mm; GE: 0.072 mm). Conclusion: The precision of the new CT-RSA software system, V3MA, is comparable to that of CTMA under zero-motion assumptions. Minor, clinically irrelevant, inter-scanner differences in CT-RSA precision exist for both software systems.

• Øhrn, Frank-David; Engseth, Lars; Pripp, Are Hugo; Schulz, Anselm & Röhrl, Stephan Maximilian (2025). Precision of computer tomography based RSA on femoral implants in total knee arthroplasty: A porcine cadaver study. Clinical Biomechanics. ISSN 0268-0033. 123, p. 1–4. doi: 10.1016/j.clinbiomech.2025.106456. Full text in Research Archive Show summary

  Background: Radiostereometric analysis is the gold standard for assessing migration of orthopaedic implants. The novel CT-based radiostereometric analysis yields high precision of evaluation of tibial implants. We analyzed the precision of CT-based radiostereometric analysis on femoral implants in knee arthroplasty at different dose levels, and compared it to previously published results on tibial implants and the available literature on precision of radiostereometric analysis. Methods: We performed a total knee arthroplasty on a porcine cadaver knee. In the subsequent 7 CT scans, we analyzed the precision of the CT-based radiostereometric analysis method in 21 samples at two different effective doses (standard and low dose), and compared this to literature on radiostereometric analysis. Findings: CT-based radiostereometric analysis of maximum total point motion of femoral and tibial components showed a precision difference of (mean, 95 % confidence interval) 0.18 mm (0.13 to 0.22), P < 0.001. For femoral implants (mean, 95 % confidence interval, standard deviation) we found precisions of 0.25 mm (0.21-0.29, 0.1) and 0.29 (0.25-0.32, 0.08) mm for the standard and low dose protocols respectively. Variability ratios of tibia versus femur and standard versus low dose femur (95 % confidence interval) were 18.3 (7.4-45.1) and 0.7 (0.3-1.7) with respective P-values of <0.001 and 0.40. Interpretation: CT-based radiostereometric analysis on femoral implants in total knee arthroplasty is feasible and has a lower, yet still acceptable, precision compared to CT-based radiostereometric analysis on tibial implants in a porcine cadaver. However, confirmation in clinical studies is warranted.

• Engseth, Lars; Øhrn, Frank-David; Schulz, Anselm & Röhrl, Stephan Maximilian (2025). CT-based migration analysis of a tibial component compared to radiostereometric analysis : one-year results of a prospective single-group implant safety study. The Bone & Joint Journal. ISSN 2049-4394. 107-B(2), p. 173–180. doi: 10.1302/0301-620X.107B2.BJJ-2024-0356.R2. Full text in Research Archive Show summary

  Aims Radiostereometric analysis (RSA) is considered the gold standard for in vivo migration analysis, but CT-based alternatives show comparable results in the shoulder and hip. We have previously validated a CT-based migration analysis method (CTMA) in a knee phantom compared to RSA. In this study, we validated the method in patients undergoing total knee arthroplasty (TKA). Our primary outcome measure was the difference in maximum total point motion (MTPM) between the differing methods. Methods A total of 31 patients were prospectively studied having undergone an uncemented medial pivot knee TKA. Migrations were measured up to 12 months with marker-based and model-based RSA, and CT-RSA. Results Mean precision data for MTPM were 0.27 mm (SD 0.09) for marker-based RSA, 0.37 mm (SD 0.26) for model-based RSA, and 0.25 mm (SD 0.11) for CTMA. CTMA was as precise as both RSA methods (p = 0.845 and p = 0.156). At three months, MTPM showed a mean of 0.66 mm (95% CI 0.52 to 0.81) for marker-based RSA, 0.79 (95% CI 0.64 to 0.94) for model-based RSA, and 0.59 (95% CI 0.47 to 0.72) for CTMA. There was no difference between CTMA and marker-based RSA (p = 0.400), but CTMA showed lower migration than model-based RSA (p = 0.019). At 12 months, MTPM was 1.03 (95% CI 0.79 to 1.26) for marker-based RSA, 1.02 (95% CI 0.79 to 1.25) for model-based RSA, and 0.71 (95% CI 0.48 to 0.94) for CTMA. MTPM for CTMA was lower than both RSA methods (p < 0.001). Differences between migration increased between the methods from three to 12 months. Mean effective radiation doses per examination were 0.016 mSv (RSA) and 0.069 mSv (CT). Imaging time for performing RSA radiographs was 17 minutes 26 seconds (SD 7 mins 9 sec) and 4 minutes 24 seconds (SD 2 mins 3 sec) for CT. Conclusion No difference in precision was found between CTMA and marker- or model-based RSA, but CTMA shows lower migration values of the tibial component at 12 months. CTMA can be used with low effective radiation doses, and CT image acquisition is faster to perform than RSA methods and may be suitable for use in ordinary clinical settings.

• Høgevold, Magnus; Alm, Carl Erik; Wright, Bryan Joseph; Ragan, Lydia; Frihagen, Frede & Röhrl, Stephan Maximilian [Show all 8 contributors for this article] (2025). The impact on lateral wall fractures by a sliding hip screw device in trochanteric fractures a biomechanical study. Bone & Joint Open (BJO). 6(5), p. 582–589. doi: 10.1302/2633-1462.65.BJO-2024-0266.R1. Full text in Research Archive Show summary

  Aims Trochanteric fractures with a reduced lateral wall thickness and a detached lesser trochanter are unstable. These characteristics can lead to failure through a lateral wall fracture after fixation with a sliding hip screw device (SHS). However, the precise mechanism by which these characteristics contribute to lateral wall fractures remains unclear. Accordingly, we examined the impact on failure by incremental decrease of both lateral wall thickness and lesser trochanter attachment in trochanteric fracture fixation using a SHS ex vivo. Methods We tested 14 pairs of embalmed femora, randomly assigned to four osteotomy groups, each representing a specific 31A1 or 31A2 fracture pattern according to the AO/Orthopaedic Trauma Association (OTA) classification. After fixation with a SHS, the specimens underwent quasi-static and dynamic axial compression until failure. Outcome measures included stiffness, deformation, load to failure, and failure pattern following a set protocol. Results We found lateral wall fractures in ten out of 28 specimens. Specimens with a thin lateral wall and a detached lesser trochanter exhibited both a significantly higher rate of lateral wall fractures (5/7 vs 5/21, p = 0.023) and a lower load to failure than specimens with only one or none of these characteristics (1,673 N (SD 810) vs 2,922 N (SD 897), p = 0.003). The specimens with a detached lesser trochanter themselves demonstrated a significantly higher rate of lateral wall fractures than those with an attached lesser trochanter (9/14 vs 1/14, p = 0.004). Conclusion Our findings emphasize the role of a detached lesser trochanter in initiating lateral wall fractures, with a reduction in load to failure when combined with reduced lateral wall thickness. Biomechanically, this suggests a failure mechanism whereby placing a load-sharing implant could overload a fragile lateral wall in unstable trochanteric fractures.

• Randers, Engelke Marie; Kibsgård, Thomas Johan; Nogueira, Liebert Parreiras; Kjensjord, Trygve; Röhrl, Stephan Maximilian & Nordsletten, Lars [Show all 7 contributors for this article] (2024). Osseointegration of minimally invasive sacroiliac joint fixation implants—A human retrieval study. Journal of Orthopaedic Research. ISSN 0736-0266. 42, p. 1820–1830. doi: 10.1002/jor.25820. Full text in Research Archive Show summary

  Minimally invasive sacroiliac joint fusion has become increasingly prevalent and is described to reduce pain and improve function. In some patients, pain can recur several months after primary surgery. Lack of early implant osseointegration might be a cause of pain and hence an indication for revision surgery. Triangular titanium implants are the most documented implant for minimally invasive sacroiliac joint fusion. There is, however, no knowledge of how triangular titanium implants osseointegrate in humans and whether fusion is induced over the sacroiliac joint. During planned revision surgery due to recurrent pain, six triangular titanium implants were retrieved from six different patients at median 9 months from primary surgery. All six implants were scanned using microcomputed tomography. The presence or absence of bone in-growth, on-growth, and through-growth of the implants was evaluated as an indication of implant osseointegration. Three of six implants showed no or minor signs of osseointegration. Of the three remaining implants, one showed partial osseointegration and two implants showed high degrees of osseointegration. This study showed that triangular titanium implants can osseointegrate into host bone in humans. When osseointegration occurs, triangular titanium implants can give fusion across the sacroiliac joint.

• Alm, Carl Erik; Karlsten, Anders; Madsen, Jan Erik; Nordsletten, Lars; Brattgjerd, Jan Egil & Pripp, Are Hugo [Show all 8 contributors for this article] (2024). No benefit of the trochanteric stabilizing plate on loss of fracture reduction in AO/OTA 31-A2 trochanteric fractures a randomized controlled trial using radiostereometric analysis. Bone & Joint Open (BJO). 5(1), p. 37–45. doi: 10.1302/2633-1462.51.BJO-2023-0082.R1. Full text in Research Archive Show summary

  Aims Despite limited clinical scientific backing, an additional trochanteric stabilizing plate (TSP) has been advocated when treating unstable trochanteric fractures with a sliding hip screw (SHS). We aimed to explore whether the TSP would result in less post operative fracture motion, compared to SHS alone. Methods Overall, 31 patients with AO/OTA 31-A2 trochanteric fractures were randomized to either a SHS alone or a SHS with an additional TSP. To compare postoperative fracture motion, radiostereometric analysis (RSA) was performed before and after weightbearing, and then at four, eight, 12, 26, and 52 weeks. With the “after weightbearing” images as baseline, we calculated translations and rotations, including shortening and medialization of the femoral shaft. Results Similar migration profiles were observed in all directions during the course of healing. At one year, eight patients in the SHS group and 12 patients in the TSP group were available for analysis, finding a clinically non-relevant, and statistically non-significant, difference in total translation of 1 mm (95% confidence interval -4.7 to 2.9) in favour of the TSP group. In line with the migration data, no significant differences in clinical outcomes were found. Conclusion The TSP did not influence the course of healing or postoperative fracture motion compared to SHS alone. Based on our results, routine use of the TSP in AO/OTA 31-A2 trochanteric fractures cannot be recommended. The TSP has been shown, in biomechanical studies, to increase stability in sliding hip screw constructs in both unstable and intermediate stable trochanteric fractures, but the clinical evidence is limited. This study showed no advantage of the TSP in unstable (AO 31-A2) fractures in elderly patients when fracture movement was evaluated with radiostereometric analysis.

• Randers, Engelke Marie; Gerdhem, Paul; Stuge, Britt Karin; Diarbakerli, Elias; Nordsletten, Lars & Röhrl, Stephan Maximilian [Show all 7 contributors for this article] (2024). The effect of minimally invasive sacroiliac joint fusion compared to sham operation: a double-blind randomized placebo-controlled trial. EClinicalMedicine. 68. doi: 10.1016/j.eclinm.2024.102438. Full text in Research Archive Show summary

  Background Minimally invasive fusion of the sacroiliac joint as treatment for low back pain may reduce pain and improve function compared to non-operative treatment, although clear evidence is lacking. The aim of this trial was to evaluate the effect of minimally invasive sacroiliac joint fusion compared to sham surgery on sacroiliac joint pain reduction. Methods In this double-blind randomized sham surgery-controlled trial patients with clinical diagnosis of sacroiliac joint pain confirmed with sacroiliac joint injection were included at two university hospitals in Sweden and Norway. Patients were randomized by the operating surgeon at each site to minimally invasive sacroiliac joint fusion or sham surgery. The primary endpoint was group difference in sacroiliac joint pain on the operated side at six months postoperatively, measured by the Numeric Rating Scale (0–10). Un-blinding and primary analysis were performed when all patients had completed six months follow-up. The trial is closed for new participants and was registered at clinicaltrials.gov : NCT03507049 . Findings Between September 1st, 2018 and October 22nd, 2021, 63 patients were randomized, 32 to the surgical group, 31 to the sham group. Mean age was 45 years (range 26–63) and 59 of 63 (94%) patients were female. The mean reduction in the operated sacroiliac joint from baseline to six months postoperative was 2.6 Numeric Rating Scale points in the surgical group and 1.7 points in the sham group (mean between groups difference −1.0 points; 95% CI, −2.2 to 0.3; p = 0.13). Interpretation This double-blind randomized controlled trial could not prove that minimally invasive fusion of the sacroiliac joint was superior to sham surgery at six months postoperative. Funding Sophies Minde Ortopedi supported a clinical research position for Engelke Marie Randers. Region Stockholm supported the cost for the Swedish ethical application and a clinical research appointment for Paul Gerdhem.

• Øhrn, Frank-David; Engseth, Lars; Pripp, Are Hugo; Röhrl, Stephan Maximilian & Schulz, Anselm (2023). Dose reduction does not impact the precision of CT-based RSA in tibial implants: a diagnostic accuracy study on precision in a porcine cadaver. Acta Orthopaedica. ISSN 1745-3674. 94, p. 550–554. doi: 10.2340/17453674.2023.24022. Full text in Research Archive Show summary

  Background and purpose: Radiostereometric analysis (RSA) is the gold standard for evaluation of migration of implants. CT-RSA has been shown to have precision at the level of RSA in hip, shoulder, and knee joint replacements. We aimed to assess the impact of dose reduction on precision of CT-RSA on tibial implants, comparing it with previously published data on precision of standard dose CT-RSA on tibial implants. Material and methods: We performed a total knee arthroplasty on a porcine knee cadaver, and subsequent CT-RSA with low effective doses (0.02 mSv). We compared the results with previously published CT-RSA data with standard (0.08 mSv) dose. The primary outcome variable was the difference in precision of the maximum total translation (MTT). Secondary variables included ratios of variances and standard deviations, and precision of peripheral point translations, center-of-mass translations, and rotations. A difference of more than 0.1 mm in precision was defined as clinically relevant. Our hypothesis was that precisions of low and standard CT-RSA doses were equal. Results: Low dose (mean 0.07, 95% confidence interval [CI] 0.06–0.08) and standard dose CT-RSA (0.08, CI 0.07–0.09) achieve similar precision, with difference in precision of MTT of 0.01, CI 0.00–0.02 mm. The F-statistic (0.99, CI 0.63–1.55) and sdtest (1.05, CI 0.43–2.58) also supported this. Conclusion: We conclude that the precision of low dose CT-RSA for tibial implants on a porcine cadaver is equal to standard dose CT-RSA. However, these findings should be confirmed in clinical trials.

• Engseth, Lars; Grønsund, Jørgen; Aunan, Eirik; Brattgjerd, Jan Egil; Schulz, Anselm & Moatshe, Gilbert [Show all 7 contributors for this article] (2023). A novel instrument for ligament balancing: a biomechanical study in human cadaveric knees. Journal of Experimental Orthopaedics. 10(1). doi: 10.1186/s40634-023-00643-7. Full text in Research Archive Show summary

  Purpose: Ligament balancing is a prerequisite for good function and survival in total knee arthroplasty (TKA). Various balancing techniques exist, but none have shown superior results. The pie-crusting technique by Bellemans of the medial collateral ligament is commonly utilized; however, it can be difficult to achieve repeatable ligament lengthening with this technique. Therefore, we invented a novel instrument to standardize the pie-crusting technique of the superficial and deep medial collateral ligament (hereafter MCL). The purpose was to examine if pie-crusting with the instrument could produce repeatable ligament lengthening. Methods: The MCL was isolated in 16 human cadaveric knees, and subjected to axial tension. The instrument was composed of a specific grid of holes in rows, used to guide sequential pie-crusting puncturing of the MCL with a Ø1.6 mm end-cutting cannula. Ligament lengthening was measured after each row of punctures. Regression analysis was performed on the results. Results: Mean lengthening ± SD in human cadaveric MCL for puncturing of row 1 in the instrument was 0.06 ± 0.09 mm, 0.06 ± 0.04 mm for row 2, 0.09 ± 0.08 mm for row 3, 0.06 ± 0.05 mm for row 4 and 0.06 ± 0.04 mm for row 5, giving a mean total lengthening of 0.33 ± 0.20 mm. Linear regression revealed that MCLs were repeatably lengthened by 0.07 mm per row when punctured using the instrument. Conclusions: MCLs showed linear lengthening in human cadavers for subsequent use of the instrument. Our instrument shows promising results for repeatable ligament lengthening.

• Rivrud, Sean C. S.; Röhrl, Stephan Maximilian & Leeuwen, Justin Arlen Maarten Joséphus (2023). Effects of patient-specific positioning guides (PSPGs) vs. conventional instrumentation on patient-reported outcome in total knee arthroplasty: secondary analysis of a randomized controlled trial after 5 years. Acta Orthopaedica. ISSN 1745-3674. 94, p. 354–359. doi: 10.2340/17453674.2023.15335. Full text in Research Archive Show summary

  Background and purpose: The use of patient-specific positioning guides (PSPGs) in total knee arthroplasty (TKA) has been advocated as a means of improving patient outcomes, but the reception of PSPGs has been mixed. The aim of our study was to compare patient-reported outcomes (KOOS, NRS-11, EQ-5D-3L, EQ-VAS) after TKA using PSPG with conventional instrumentation (CI) to determine whether there is a discernible clinical benefit to using PSPGs. Patients and methods: This multicenter randomized controlled trial (RCT) followed 77 patients who were randomly assigned to 1 of 2 cohorts between September 2011 and January 2014-one receiving TKA with PSPGs (from Materialise NV) and one receiving TKA with CI-with each cohort followed up until 5 years after the operation. The Vanguard Cruciate Retaining Total Knee System and Refobacin Bone Cement R were used in all operations. KOOS was evaluated using confidence intervals, with differences of less than 10 KOOS units between the cohorts interpreted as indicating the absence of a clinically meaningful difference. Results: No significant differences were found in any of the measured clinical outcomes-KOOS, NRS-11, EQ-5D-3L, EQ-VAS, range of motion, or radiolucent lines scoring-between the cohort operated on using PSPG and the cohort operated on using CI after 5 years of follow-up. Conclusion: There was no statistically significant effect of PSPGs on patient-reported outcomes or range of motion in TKA.

• Poulsen, Magnus; Stødle, Are Haukåen; Nordsletten, Lars & Röhrl, Stephan Maximilian Herbert (2023). CT-based radiostereometric analysis for assessing midfoot kinematics: precision compared with marker-based radiostereometry. Acta Orthopaedica. ISSN 1745-3674. 94, p. 366–372. doi: 10.2340/17453674.2023.16905. Full text in Research Archive Show summary

  Background and purpose: 3-dimensional midfoot motion is hard to evaluate in clinical practice. We present a new computed tomography (CT)-based radiostereometric analysis (CT-RSA) technique to examine in vivo midfoot kinematics during single-leg stance and compare it with marker-based radiostereometry (RSA).Patients and methods: 8 patients were examined with bilateral non- and full-weight-bearing CT images of the midfoot. 1st tarsometatarsal motion was analyzed using a surface-registration technique (CT-RSA). As all patients had unilateral tantalum markers in the 1st cuneiform (C1) and 1st metatarsal (M1), comparison of precision with markerbased RSA was performed. CT-RSA precision was evaluated with surface registration of both C1–M1 bone and C1–M1 tantalum markers, while RSA precision was determined with C1–M1 markers only. Additionally, to remove motion bias, we evaluated intrasegmental CT-RSA precision by comparing proximal with distal part of M1.Results: Under physical load, the primary movement for the 1st tarsometatarsal joint was M1 dorsiflexion (mean 1.4°), adduction (mean 1.4°), and dorsal translation (mean 1.1 mm). CT-RSA precision, using surface bone or markers, was in the range of 0.3–0.7 mm for translation and 0.6–1.6° for rotation. In comparison, RSA precision was in the range of 0.4–0.9 mm for translation and 1.0–1.7° for rotation. Finally, intrasegmental CT-RSA precision was in the range of 0.1–0.2 mm for translation and 0.4–0.5° for rotation.Conclusion: CT-RSA is a valid and precise, non-invasive method to measure midfoot kinematics when compared with conventional RSA.

• Engseth, Lars; Schulz, Anselm; Pripp, Are Hugo; Röhrl, Stephan Maximilian & Øhrn, Frank-David (2023). CT-based migration analysis is more precise than radio-stereometric analysis for tibial implants: a phantom study on a porcine cadaver. Acta Orthopaedica. ISSN 1745-3674. 94, p. 207–214. doi: 10.2340/17453674.2023.12306. Full text in Research Archive Show summary

  Background and purpose: Radiostereometric analysis (RSA) is the gold standard for migration analysis, but computed tomography analysis methods (CTRSA) have shown comparable results in other joints. We attempted to validate precision for CT compared with RSA for a tibial implant. Material and methods: RSA and CT were performed on a porcine knee with a tibial implant. Marker-based RSA, model-based RSA (MBRSA), and CT scans from 2 different manufacturers were compared. CT analysis was performed by 2 raters for reliability evaluation. Results: 21 double examinations for precision measurements for RSA and CT-based Micromotion Analysis (CTMA) were analysed. Mean (95% confidence interval) precision data for maximum total point motion (MTPM) using marker-based RSA was 0.45 (0.19–0.70) and 0.58 (0.20–0.96) using MBRSA (F-statistic 0.44 [95% CI 0.18–1.1], p = 0.07). Precision data for total translation (TT) for CTMA was 0.08 (0.03–0.12) for the GE scanner and 0.11 (0.04–0.19) for the Siemens scanner (F-statistic 0.37 [0.15–0.91], p = 0.03). When comparing the aforementioned precision for both RSA methods with both CTMA analyses, CTMA was more precise (p < 0.001). The same pattern was seen for other translations and migrations. Mean effective radiation doses were 0.005 mSv (RSA) (0.0048–0.0050) and 0.08 mSv (CT) (0.078–0.080) (p < 0.001). Intra- and interrater reliability were 0.79 (0.75–0.82) and 0.77 (0.72–0.82), respectively. Conclusion: CTMA is more precise than RSA for migration analysis of a tibial implant, has overall good intra- and interrater reliability but higher effective radiation doses in a porcine cadaver.

• Poulsen, Magnus; Stødle, Are Haukåen; Nordsletten, Lars & Röhrl, Stephan Maximilian Herbert (2022). Does temporary bridge plate fixation preserve joint motion after an unstable Lisfranc injury? Foot and Ankle Surgery. ISSN 1268-7731. p. 1–7. doi: 10.1016/j.fas.2022.12.007. Full text in Research Archive Show summary

  Background Recently, temporary bridge plate fixation has gained popularity in the treatment of unstable Lisfranc injuries. The technique aims to reduce the risk of posttraumatic osteoarthritis, and after plate removal, the goal is to regain joint mobility. Here we explore marker-based radiostereometric analysis (RSA) to measure motion in the 1st tarsometatarsal (TMT) joint and asses the radiological outcome in patients treated with this surgical technique. Method Ten patients with an unstable Lisfranc injury were included. All were treated with a dorsal bridge plate over the 1st TMT joint and primary arthrodesis of the 2nd and 3rd TMT joints. The plate was removed four months postoperatively. Non- and weight-bearing RSA images were obtained one and five years postinjury to assess joint mobility and signs of osteoarthritis. Results Detectable 1st TMT joint motion was observed in 2/10 patients after one year, and 6/9 patients after five years. At the final follow-up, mean 1st TMT dorsiflexion was 2.0°. Radiologically, the incidence of posttraumatic osteoarthritis was present in 4/10 patients after one year, and 5/9 patients after five years. All patients had observed TMT joint stability throughout the follow-up period. Conclusion Preservation of joint motion can be achieved with a temporary bridge plate fixation over the 1st TMT joint. Type of study/level of evidence Prospective cohort study/Therapeutically level IV.

• Thoen, Peder Svenkerud; Lygre, Stein Håkon Låstad; Nordsletten, Lars; Furnes, Ove Nord; Stigum, Hein & Hallan, Geir [Show all 7 contributors for this article] (2022). Risk factors for revision surgery due to dislocation within 1 year after 111,711 primary total hip arthroplasties from 2005 to 2019: a study from the Norwegian Arthroplasty Register. Acta Orthopaedica. ISSN 1745-3674. 93, p. 593–601. doi: 10.2340/17453674.2022.3474. Full text in Research Archive Show summary

  Dislocation of a hip prosthesis is the 3rd most frequent cause (after loosening and infection) for hip revision in Norway. Recently there has been a shift in surgical practice including preferred head size, surgical approach, articulation, and fixation. We explored factors associated with the risk of revision due to dislocation within 1 year and analyzed the impact of changes in surgical practice. Patients and methods: 111,711 cases of primary total hip arthroplasty (THA) from the Norwegian Arthroplasty Register were included (2005–2019) after primary THA with either 28 mm, 32 mm, or 36 mm femoral heads, or dualmobility articulations. A flexible parametric survival model was used to calculate hazard ratios for risk factors. Kaplan–Meier survival rates were calculated. Results: There was an increased risk of revision due to dislocation with 28 mm femoral heads (HR 2.6, 95% CI 2.0–3.3) compared with 32 mm heads. Furthermore, there was a reduced risk of cemented fixation (HR 0.6, CI 0.5–0.8) and reverse hybrid (HR 0.6, CI 0.5–0.8) compared with uncemented. Also, both anterolateral (HR 0.5, CI 0.4–0.7) and lateral (HR 0.6, CI 0.5–0.7) approaches were associated with a reduced risk compared with the posterior approach. The time-period 2010–2014 had the lowest risk of revision due to dislocation. The trend during the study period was towards using larger head sizes, a posterior approach, and uncemented fixation for primary THA. Interpretation: Patients with 28 mm head size, a posterior approach, or uncemented fixation had an increased risk of revision due to dislocation within 1 year after primary THA. The shift from lateral to posterior approach and more uncemented fixation was a plausible explanation for the increased risk of revision due to dislocation observed in the most recent time-period. The increased risk of revision due to dislocation was not fully compensated for by increasing femoral head size from 28 to 32 mm.

• Glad, Trygve Andreas Holm; Røkkum, Magne; Röhrl, Stephan Maximilian Herbert; Roness, Siri Pernille; Godang, Kristin & Reigstad, Ole (2022). A randomized controlled trial comparing two modern total wrist arthroplasties : improved function with stable implants, but high complication rates in non-rheumatoid wrists at two years. The Bone & Joint Journal. ISSN 2049-4394. 104-B(10), p. 1132–1141. doi: 10.1302/0301-620X.104B10.BJJ-2022-0201.R2. Full text in Research Archive
• Alm, Carl Erik; Gjertsen, Jan-Erik; Basso, Trude; Matre, Kjell; Röhrl, Stephan Maximillian & Madsen, Jan Erik [Show all 7 contributors for this article] (2021). Trochanteric stabilizing plate in the treatment of trochanteric fractures: a scoping review. Acta Orthopaedica. ISSN 1745-3674. 92, p. 1–6. doi: 10.1080/17453674.2021.1954305. Full text in Research Archive Show summary

  Background and purpose — The trochanteric stabilizing plate (TSP) may be used as an adjunct to a sliding hip screw (SHS) in the treatment of trochanteric fractures to increase construct stability. We performed a scoping review of the literature to clarify when and how the TSP may be useful. Methods — A systematic search was performed in 5 databases and followed by a backwards-and-forwards citation search of the identified papers. 24 studies were included. Results — 6 biomechanical studies and 18 clinical studies were included in the review. The studies presented mainly low-level evidence. All studies were on unstable trochanteric fractures or fracture models. Due to the heterogeneity of methods and reporting, we were not able to perform a meta-analysis. In the biomechanical trials, the TSP appeared to increase stability compared with SHS alone, up to a level comparable with intramedullary nails (IMNs). We identified 1,091 clinical cases in the literature where a TSP had been used. There were 82 (8%) reoperations. The rate of complications and reoperations for SHS plus TSP was similar to previous reports on SHS alone and IMN. It was not possible to conclude whether the TSP gave better clinical results, when compared with either SHS alone or with IMN. Interpretation — The heterogeneity of methods and reporting precluded any clear recommendations on when to use the TSP, or if it should be used at all.

• Leta, Tesfaye Hordofa; Gjertsen, Jan-Erik; Dale, Håvard; Hallan, Geir; Lygre, Stein Håkon Låstad & Fenstad, Anne Marie [Show all 26 contributors for this article] (2021). Antibiotic-loaded bone cement in prevention of periprosthetic joint infections in primary total knee arthroplasty: A register-based multicentre randomised controlled non-inferiority trial (ALBA trial). BMJ Open. 11:e41096, p. 1–8. doi: 10.1136/bmjopen-2020-041096. Full text in Research Archive Show summary

  Introduction The current evidence on the efficacy of antibiotic-loaded bone cement (ALBC) in reducing the risk of periprosthetic joint infections (PJI) after primary joint reconstruction is insufficient. In several European countries, the use of ALBC is routine practice unlike in the USA where ALBC use is not approved in low-risk patients. Therefore, we designed a double-blinded pragmatic multicentre register-based randomised controlled non-inferiority trial to investigate the effects of ALBC compared with plain bone cement in primary total knee arthroplasty (TKA). Methods and analysis A minimum of 9,172 patients undergoing full-cemented primary TKA will be recruited and equally randomised into the ALBC group and the plain bone cement group. This trial will be conducted in Norwegian hospitals that routinely perform cemented primary TKA. The primary outcome will be risk of revision surgery due to PJI at 1-year of follow-up. Secondary outcomes will be: risk of revision due to any reason including aseptic loosening at 1, 6, 10 and 20 years of follow-up; patient-related outcome measures like function, pain, satisfaction and health-related quality of life at 1, 6 and 10 years of follow-up; risk of changes in the microbial pattern and resistance profiles of organisms cultured in subsequent revisions at 1, 6, 10 and 20 years of follow-up; cost-effectiveness of routine ALBC versus plain bone cement use in primary TKA. We will use 1:1 randomisation with random permuted blocks and stratify by participating hospitals to randomise patients to receive ALBC or plain bone cement. Inclusion, randomisation and follow-up will be through the Norwegian Arthroplasty Register.

• Øhrn, Frank-David; Lian, Øystein Bjerkestrand; Tsukanaka, Masako & Röhrl, Stephan Maximillian (2021). Early migration of a medially stabilized total knee arthroplasty : a radiostereometric analysis study up to two years. Bone & Joint Open (BJO). 2(9), p. 737–744. doi: 10.1302/2633-1462.29.BJO-2021-0115.R1. Full text in Research Archive Show summary

  Aims Medial pivot (MP) total knee arthroplasties (TKAs) were designed to mimic native knee kinematics with their deep medial congruent fitting of the tibia to the femur almost like a ball-on- socket, and a flat lateral part. GMK Sphere is a novel MP implant. Our primary aim was to study the migration pattern of the tibial tray of this TKA. Methods A total of 31 patients were recruited to this single-group radiostereometric analysis (RSA) study and received a medial pivot GMK Sphere TKA. The distributions of male patients versus female patients and right versus left knees were 21:10 and 17:14, respectively. Mean BMI was 29 kg/m2 (95% confidence interval (CI) 27 to 30) and mean age at surgery was 63 years (95% CI 61 to 66). Maximum total point motions (MTPMs), medial, proximal, and anterior translations and transversal, internal, and varus rotations were calculated at three, 12, and 24 months. Patient-reported outcome measure data were also retrieved. Results MTPMs at three, 12, and 24 months were 1.0 mm (95% CI 0.8 to 1.2), 1.3 mm (95% CI 0.9 to 1.7), and 1.4 mm (0.8 to 2.0), respectively. The Forgotten Joint Score was 79 (95% CI 39 to 95) and Knee Injury and Osteoarthritis Outcome Score obtained at two years was 94 (95% CI 81 to 100), 86 (95% CI 75 to 93), 94 (95% CI 88 to 100), 69 (95% CI 48 to 88), and 81 (95% CI59 to 100) for Pain, Symptoms, Activities of Daily Living, Sport & Recreation, and Quality of Life, respectively. Conclusion In conclusion, we found that the mean increase in MTPM was lower than 0.2 mm between 12 and 24 months and thus apparently stable. Yet the GMK Sphere had higher migration at one and two years than anticipated. Based on current RSA data, we therefore cannot conclude on the long-term performance of the implant, pending further assessment.

• Fraser, Alexander Nilsskog; Bøe, Berte Marie Grimsmo; Fjalestad, Tore; Madsen, Jan Erik & Röhrl, Stephan Maximillian (2021). Stable glenoid component of reverse total shoulder arthroplasty at 2 years as measured with model-based radiostereometric analysis (RSA). Acta Orthopaedica. ISSN 1745-3674. 92(6), p. 644–650. doi: 10.1080/17453674.2021.1943932. Full text in Research Archive Show summary

  Background and purpose — Reverse total shoulder arthroplasty (TSA) is used for treating cuff arthropathy, displaced proximal humeral fractures (PHF), and in revision shoulder surgery, despite sparse evidence on long-term results. We assessed stability of the glenoid component in reverse TSA, using model-based RSA. Patients and methods — 20 patients (mean age 76 years, 17 female), operated on with reverse TSA at Oslo University Hospital, in 2015–2017 were included. Indications for surgeries were PHFs, malunion, cuff arthropathy, and chronic shoulder dislocation. RSA markers were placed in the scapular neck, the coracoid, and the acromion. RSA radiographs were conducted postoperatively, at 3 months, 1 year, and 2 years. RSA analysis was performed using RSAcore with Reversed Engineering (RE) modality, with clinical precision < 0.25 mm for all translations (x, y, z) and < 0.7° for rotations (x, z). Scapular “notching” was assessed in conventional radiographs. Results — 1 patient was excluded due to revision surgery. More than half of the patients displayed measurable migration at 2 years: 6 patients with linear translations below 1 mm and 8 patients who showed rotational migration. Except for one outlier, the measured rotations were below 2°. The migration pattern suggested implant stability at 2 years. 10 patients showed radiolographic signs of “notching”, and the mean Oxford Shoulder Score (OSS) at 2 years was 29 points (15–36 points). Interpretation — Stability analysis of the glenoid component of reversed total shoulder arthroplasty using reversed engineering (RE) model-based RSA indicated component stability at 2 years.

• Halvorsen, Vera Baasland; Fenstad, Anne Marie; Röhrl, Stephan Maximillian; Engesæter, Lars B.; Nordsletten, Lars & Terjesen, Terje [Show all 8 contributors for this article] (2020). Hoftelidelser hos barn og unge- utredning og behandling av senfølger. Tidsskrift for Den norske legeforening (Tidsskriftet). ISSN 0029-2001. 17. doi: 10.4045/tidsskr.20.0274. Full text in Research Archive Show summary

  Følgene av hoftesykdom og hofteskader hos barn og unge kan kreve kirurgisk intervensjon. Leddbevarende inngrep utført i 12–21-årsalderen gir ofte gode langtidsresultater og kan utsette behovet for proteseinngrep. Hos pasienter under 21 år er mer enn 90 % av de moderne hofteprotesene som er satt inn de siste to tiårene, intakte etter ti år. Alvorlige hoftesymptomer og røntgenologiske forandringer i eller rundt hofteleddet hos barn og unge representerer en ortopedisk utfordring. Det kan være pasienter med følgetilstander etter hoftedysplasi, Calvé-Legg-Perthes’ sykdom (CLP), idiopatisk avaskulær nekrose av caput femoris (AVN), glidning av caput femoris i fysen (SCFE), femoroacetabulær inneklemming (femoroacetabular impingement, FAI), lårhals- eller bekkenbrudd eller pyogene artritter. Noen av tilstandene kan i løpet av få år medføre store patologiske forandringer i caput femoris, i en del tilfeller også i acetabulum (hofteleddskålen), slik at pasientene får betydelige smerter og stor funksjonsnedsettelse. Å fjerne de patologiske forandringene og implantere hofteprotese er mindre aktuelt hos de svært unge pasientene, siden de risikerer flere revisjonsinngrep i løpet av livet. Formålet med artikkelen er å gi en oversikt over utredning og behandling av senfølgene av disse hoftelidelsene hos pasienter i aldersgruppen 12–21 år, og å redegjøre for langtidsresultatene etter leddbevarende kirurgi og etter proteseinnsetting. Kunnskapsgrunnlaget baserer seg på forfatternes kliniske erfaringer og vitenskapelige studier som omhandler resultatene av konservativ behandling og hofteleddmodifiserende kirurgi med minst ti års oppfølging.

• Thoen, Peder Svenkerud; Nordsletten, Lars; Pripp, Are Hugo & Röhrl, Stephan Maximillian (2020). Results of a randomized controlled trial with five-year radiostereometric analysis results of vitamin E-infused highly crosslinked versus moderately crosslinked polyethylene in reverse total hip arthroplasty. The Bone & Joint Journal. ISSN 2049-4394. 102-B(12), p. 1646–1653. doi: 10.1302/0301-620X.102B12.BJJ-2020-0721.R1. Full text in Research Archive Show summary

  Aims Vitamin E-infused highly crosslinked polyethylene (VEPE) has been introduced into total hip arthroplasty (THA) with the aim of further improving the wear characteristics of moderately and highly crosslinked polyethylenes (ModXLPE and HXLPE). There are few studies analyzing the outcomes of vitamin E-infused components in cemented arthroplasty, though early acetabular component migration has been reported. The aim of this study was to measure five-year polyethylene wear and acetabular component stability of a cemented VEPE acetabular component compared with a ModXLPE cemented acetabular component. Methods In a prospective randomized controlled trial (RCT), we assessed polyethylene wear and acetabular component stability (primary outcome) with radiostereometric analysis (RSA) in 68 patients with reverse hybrid THA at five years follow-up. Patients were randomized to either a VEPE or a ModXLPE cemented acetabular component. Results Mean polyethylene wear in the proximal direction was 0.17 mm (SD 0.15) for the VEPE group and 0.20 mm (SD 0.09) for the ModXLPE group (p = 0.005) at five years. Annual proximal wear rates were 0.03 mm/year (VEPE) and 0.04 mm/year (ModXLPE). Total 3D wear was 0.21 mm (SD 0.26) and 0.23 mm (SD 0.10) for the VEPE and ModXLPE groups, respectively (p = 0.009). Total 3D cup translation was 0.72 mm (SD 0.70) (VEPE) and 0.50 mm (SD 0.44) (ModXLPE) (p = 0.409). Conclusion At five years, there was less polyethylene wear in the VEPE group than in the ModXLPE group. Both VEPE and ModXLPE cemented components showed low annual wear rates. Component stability was similar in the two groups and remained constant up to five years. Whether these results will equate to a lower long-term revision rate is still unknown.

• Øhrn, Frank-David; Gøthesen, Øystein; Lygre, Stein Håkon Låstad; Peng, Yi; Lian, Øystein Bjerkestrand & Lewis, Peter L [Show all 8 contributors for this article] (2020). Decreased survival of medial pivot designs compared with cruciate-retaining designs in TKA without patellar resurfacing. Clinical Orthopaedics and Related Research. ISSN 0009-921X. 478(6), p. 1207–1218. doi: 10.1097/CORR.0000000000001120. Full text in Research Archive Show summary

  One of the authors (F-DØ) has received, during the study period, funding from the Møre and Romsdal Hospital Trust, Norway. The institution of one or more of the authors, the Center for Implant and Radiostereometric Research Oslo (CIRRO) (F-DØ, SMR) has received, during the study period, funding from from Medacta International for an ongoing RSA study on the survival of GMK® Sphere. Each of the remaining authors certify that neither they, nor anymember of their immediate families, have funding or commercial associations (consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article. Each author certifies that his institution approved the human protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research. This work was performed at Kristiansund Hospital, Møre and Romsdal Hospital Trust, Kristiansund, Norway

• Yang, Zhengming; Röhrl, Stephan Maximillian & Nordsletten, Lars (2019). Displaced Acetabular Fracture in Elderly Patients: Is Acute Arthroplasty an Effective Option? Zeitschrift für Orthopädie und Unfallchirurgie. ISSN 1864-6697. 157(6), p. 676–683. doi: 10.1055/a-0842-2320. Full text in Research Archive
• Flatøy, Bernhard; Dahl, Jon; Röhrl, Stephan Maximillian & Nordsletten, Lars (2019). Does radiopaque cement conceal periprosthetic bone loss around femoral stems? HIP International. ISSN 1120-7000. p. 1–8. doi: 10.1177/1120700019863352. Full text in Research Archive
• Brun, Ole-Christian Laahne; Sund, Helge Norheim; Nordsletten, Lars; Röhrl, Stephan Maximillian & Mjaaland, Knut Erik (2019). Component Placement in Direct Lateral vs Minimally Invasive Anterior Approach in Total Hip Arthroplasty: Radiographic Outcomes From a Prospective Randomized Controlled Trial. Journal of Arthroplasty. ISSN 0883-5403. 34(8), p. 1718–1722. doi: 10.1016/j.arth.2019.04.003. Full text in Research Archive
• Halvorsen, Vera Baasland; Fenstad, Anne Marie; Engesæter, Lars B.; Nordsletten, Lars; Overgaard, Søren & Pedersen, Alma B. [Show all 11 contributors for this article] (2019). Outcome of 881 total hip arthroplasties in 747 patients 21 years or younger: data from the Nordic Arthroplasty Register Association (NARA) 1995-2016. Acta Orthopaedica. ISSN 1745-3674. 90(4), p. 331–337. doi: 10.1080/17453674.2019.1615263. Full text in Research Archive Show summary

  Background and purpose — The literature is scarce on the outcome of the youngest patients with total hip arthroplasties (THAs). We analyzed register data, revision risk, and related factors in patients 21 years or younger with THAs in the Nordic Arthroplasty Register Association (NARA). Patients and methods — We included all THA patients 21 years or younger reported during 1995 through 2016 to the Danish, Finnish, Norwegian, and Swedish hip arthroplasty registers and merged these into the NARA dataset. Primary outcome was any implant revision. Results — We identified 881 THAs in 747 patients. Mean age at primary surgery was 18 years (9–21). The indications for THA were pediatric hip diseases (33%), systemic inflammatory disease (23%), osteoarthritis (4%), avascular necrosis (12%), hip fracture sequelae (7%), and other diagnoses (21%). Unadjusted 10-year survival for all THAs was 86%. Comparison between indications showed no differences in survival. Uncemented implants were used most frequently. Survival for uncemented and cemented implants was the same adjusted for sex, indication, head size, and time period for primary surgery. Aseptic loosening was the main cause of revision. Interpretation — Both cemented and uncemented fixations seem to be a viable option in this age group, but with a lower implant survival than in older patient groups.

• Aunan, Eirik & Röhrl, Stephan Maximillian (2018). No detrimental effect of ligament balancing on functional outcome after total knee arthroplasty: a prospective cohort study on 129 mechanically aligned knees with 3 years` follow-up. Acta Orthopaedica. ISSN 1745-3674. 89(5), p. 548–554. doi: 10.1080/17453674.2018.1485283. Full text in Research Archive
• Leeuwen, Justin Arlen Maarten Joséphus; Snorrason, Finnur & Röhrl, Stephan Maximillian (2018). No radiological and clinical advantages with patient-specific positioning guides in total knee replacement: A multicenter randomized controlled trial. Acta Orthopaedica. ISSN 1745-3674. 89(1), p. 89–94. doi: 10.1080/17453674.2017.1393732. Full text in Research Archive Show summary

  Background and purpose — Although the use of patient-specific positioning guides (PSPGs) in total knee replacement (TKR) in theory is promising, the technique has not yet proven its superior- ity compared with the conventional method. We compared radio- logical alignment and clinical outcome between TKR performed with the use of PSPGs and the conventional operation method. Patients and methods — 3 hospitals participated in a prospec- tive trial. 109 patients were randomized to either the conventional method or to the use of PSPGs. Postoperatively a full-length standing anteroposterior radiograph and a postoperative CT scan were taken. On the CT scan the alignments were measured for both the femoral and tibial components in the frontal, sagit- tal, and axial plane. The Knee injury and Osteoarthritis Outcome Score (KOOS), the Eurocol-5D-3L (Eq5D) descriptive system and visual analogue scale (VAS), a pain score (NRS), and range of motion (ROM) were recorded preoperatively, and at 3 months, 1, and 2 years. The operation time and length of hospital stay were recorded. Results — 90 patients were available for postoperative CT mea- surements. A statistically significant difference was found between the conventional TKR instrumentation and the use of PSPGs for the frontal femoral (mean (SD) 0.6° (1.7) vs. –0.3° (2.2), CI 0.08 to 1.69) and tibial (–0.3° (1.5) vs. 0.9° (2.1), CI –1.98 to –0.44) compo- nent angles and for the tibial alignment in the sagittal plane (–3.8° (3.0) vs. –2.2° (2.5), CI –2.72; –0.42). The proportions of outliers were similar between the groups as well as the hip–knee–ankle angle, the KOOS sub scores, the Eq5D, pain (NRS), ROM, opera- tion time, and length of hospital stay. Interpretation — The use of PSPGs requires a preoperative CT scan or MRI and the guides have an additional cost. As this study was not able to prove any extra benefit of the use of PSPGs we recommend the conventional operation method for TKR.

• Figved, Wender; Svenøy, Stian; Röhrl, Stephan Maximillian; Dahl, Jon; Nordsletten, Lars & Frihagen, Frede Jon (2018). Higher cartilage wear in unipolar than bipolar hemiarthroplasties of the hip at 2 years: A randomized controlled radiostereometric study in 19 fit elderly patients with femoral neck fractures. Acta Orthopaedica. ISSN 1745-3674. 89(5), p. 503–508. doi: 10.1080/17453674.2018.1475899. Full text in Research Archive Show summary

  Background and purpose: The use of unipolar hemi­arthroplasties for femoral neck fractures is increasing in some countries due to reports of higher reoperation rates in bipolar prostheses. On the other hand, it has been proposed that bipolar hemiarthroplasties have clinical advantages and less cartilage wear than unipolar hemiarthroplasties. We compared cartilage wear between bipolar and unipolar hemiarthroplasties using radiostereometric analyses (RSA), in patients aged 70 years or older. Patients and methods: 28 ambulatory, lucid patients were randomized to treatment with a unipolar or a bipolar hemiarthroplasty for an acute femoral neck fracture. Migration of the prosthetic head into the acetabulum was measured using RSA. Secondary outcomes were Harris Hip Score (HHS), and EQ-5D scores. Patients were assessed at 3, 12. and 24 months. Results: 19 patients were available for follow-up at 2 years: mean proximal penetration was 0.83 mm in the unipolar group and 0.24 mm in the bipolar group (p = 0.01). Mean total point movement was 1.3 mm in the unipolar group and 0.95 mm in the bipolar group (p = 0.3). Median HHS was 78 (62–96) in the unipolar group and 100 (70–100) in the bipolar group (p = 0.004). Median EQ-5D Index Score was 0.73 (0.52–1.00) in the unipolar group and 1.00 (0.74–1.00) in the bipolar group (p = 0.01). Median EQ-5D VAS was 70 (50–90) in the unipolar group and 89 (70–95) in the bipolar group (p = 0.03) Interpretation: Patients with unipolar hemiarthroplasties had higher proximal cartilage wear and lower functional outcomes. Unipolar hemiarthroplasties should be used with caution in ambulatory, lucid patients.

• Øhrn, Frank-David; Leeuwen, Justin Arlen Maarten Joséphus; Tsukanaka, Masako & Röhrl, Stephan Maximillian (2018). A 2-year RSA study of the Vanguard CR total knee system: A randomized controlled trial comparing patient-specific positioning guides with conventional technique. Acta Orthopaedica. ISSN 1745-3674. 89(4), p. 418–424. doi: 10.1080/17453674.2018.1470866. Full text in Research Archive Show summary

  Backgound and purpose - There is some concern regarding the revision rate of the Vanguard CR TKA in 1 registry, and the literature is ambiguous about the effi cacy of patient-specifi c positioning guides (PSPGs). The objective of this study was to investigate the stability of the cemented Vanguard CR Total Knee using 2 different surgical techniques. Our hypothesis was that there is no difference in migration when implanting the Vanguard CR with either PSPGs or conventional technique. We hereby present a randomized controlled trial of 2-year follow-up with radiostereometric analysis (RSA). Patients and methods — 40 TKAs were performed between 2011 and 2013 with either PSPGs or the conventional technique and 22 of these were investigated with RSA. Results — The PSPG (8 knees) and the conventional (14 knees) groups had a mean maximum total point motion (MTPM) (95% CI) of 0.83 (0.48–1.18) vs. 0.70 (0.43–0.97) mm, 1.03 (0.60–1.43) vs. 0.86 (0.53–1.19), and 1.46 (1.07– 1.85) vs. 0.80 (0.52–1.43) at 3, 12, and 24 months respectively (p = 0.1). 5 implants had either an MTPM > 1.6 mm at 12 months and/or a migration of more than 0.2 mm between 1- and 2-year follow-ups. 2 of these also had a peripheral subsidence of more than 0.6 mm at 2 years. Interpretation — 5 implants (3 in the PSPG group) were found to be at risk of later aseptic loosening. The PSPG group continuously migrated between 12 and 24 months. The conventional group had an initial high migration between postoperative and 3 months, but seemed more stable after 1 year. Although the difference was not statistically signifi cant, we think the migration in the PSPG group is of some concern

• Lindalen, Einar; Thoen, Peder Svenkerud; Nordsletten, Lars; Høvik, Øystein & Röhrl, Stephan Maximillian (2018). Low wear rate at 6-year follow-up of vitamin E-infused cross-linked polyethylene: a randomised trial using 32- and 36-mm heads. HIP International. ISSN 1120-7000. doi: 10.1177/1120700018798790. Full text in Research Archive
• Fraser, Alexander Nilsskog; Tsukanaka, Masako; Fjalestad, Tore; Madsen, Jan Erik & Röhrl, Stephan Maximillian (2018). Model-based RSA is suitable for clinical trials on the glenoid component of reverse total shoulder arthroplasty. Journal of Orthopaedic Research. ISSN 0736-0266. 36(12), p. 3299–3307. doi: 10.1002/jor.24111. Full text in Research Archive
• Petursson, Gunnar; Fenstad, Anne Marie; Gøthesen, Øystein; Dyrhovden, Gro Sævik; Hallan, Geir & Röhrl, Stephan Maximillian [Show all 8 contributors for this article] (2018). Computer-assisted compared with conventional total knee replacement: A Multicenter Parallel-Group Randomized Controlled Trial. Journal of Bone and Joint Surgery. American volume. ISSN 0021-9355. 100(15), p. 1265–1274. doi: 10.2106/JBJS.17.01338. Full text in Research Archive
• Glad, Trygve Andreas Holm; Reigstad, Ole; Tsukanaka, Masako; Røkkum, Magne & Röhrl, Stephan Maximillian (2018). High Precision and Accuracy of Model-Based RSA for Analysis of Wrist Arthroplasty. Journal of Orthopaedic Research. ISSN 0736-0266. 36(11), p. 3053–3063. doi: 10.1002/jor.24063. Full text in Research Archive
• Aunan, Eirik; Kibsgård, Thomas & Röhrl, Stephan Maximillian (2017). Minimal effect of patella eversion on ligament balancing in cruciate-retaining total knee arthroplasty. Archives of Orthopaedic and Trauma Surgery. ISSN 0936-8051. 137(3), p. 387–392. doi: 10.1007/s00402-017-2625-y. Full text in Research Archive Show summary

  Purpose The effect of patellar eversion on ligament laxity measurements is still unclear. The purpose of this study was to investigate the influence of patellar eversion on medial and lateral ligament laxity measurements performed intra-operatively in total knee arthroplasty (TKA). Methods A total of 49 knees (27 female) with mean age 70 years (42–83) and mean body mass index of 28.5 were operated consecutively with a cruciate-retaining prosthesis. Medial and lateral ligament laxity in extension and in 90° of flexion was measured with the spatula-method intra-operatively after implantation of the prosthetic components with the patella everted and thereafter with the patella repositioned. The corresponding changes in gap height and inclination were calculated. Results A statistically significant increase of 0.6 mm (p < 0.001) in ligament laxity (condylar lift-off) laterally in flexion was found with the patella repositioned compared to everted. No differences were found in extension or medially in flexion. Correspondingly, the flexion gap increased by 0.4 mm (p < 0.001) and the flexion gap inclination increased by 0.6° (p = 0.002) when the patella was repositioned. Conclusions Earlier research has shown that ligament laxity must be at least 1–2 mm to cause inferior function after TKA. In the current study, we found that the effect of patellar eversion on ligament laxity measurements is too small to be considered clinically relevant.

• Kibsgård, Thomas; Röhrl, Stephan Maximillian; Røise, Olav; Sturesson, Bengt & Stuge, Britt (2017). Movement of the sacroiliac joint during the Active Straight Leg Raise test in patients with long-lasting severe sacroiliac joint pain. Clinical Biomechanics. ISSN 0268-0033. 47, p. 40–45. doi: 10.1016/j.clinbiomech.2017.05.014. Full text in Research Archive
• Tsukanaka, Masako; Halvorsen, Vera Baasland; Nordsletten, Lars; Engesæter, Ingvild Øvstebø; Engesæter, Lars B. & Fenstad, Anne Marie [Show all 7 contributors for this article] (2016). Implant survival and radiographic outcome of total hip replacement in patients less than 20 years old. Acta Orthopaedica. ISSN 1745-3674. 87(5), p. 479–484. doi: 10.1080/17453674.2016.1212180. Full text in Research Archive
• Tsukanaka, Masako; Röhrl, Stephan Maximillian; Schewelov, Thord von & Nordsletten, Lars (2016). Identification of femoral head center of bipolar hemiarthroplasy in radiostereometric analysis with elementary geometrical shape models. Journal of Biomechanics. ISSN 0021-9290. 49(3), p. 469–473. doi: 10.1016/j.jbiomech.2015.11.054. Full text in Research Archive
• Otten, Volker T.C.; Crnalic, Sead; Röhrl, Stephan Maximillian; Nivbrant, Bo & Nilsson, Kjell G. (2016). Stability of Uncemented Cups - Long-Term Effect of Screws, Pegs and HA Coating: A 14-Year RSA Follow-Up of Total Hip Arthroplasty. Journal of Arthroplasty. ISSN 0883-5403. 31(1), p. 156–161. doi: 10.1016/j.arth.2015.07.012. Full text in Research Archive
• Tsukanaka, Masako; Støen, Ragnhild Øydna; Figved, Wender; Frihagen, Frede Jon; Nordsletten, Lars & Röhrl, Stephan Maximillian (2016). Steady state acetabular cartilage wear after bipolar hemiarthroplasty: a case series of 10 patients With radiostereometric analysis. HIP International. ISSN 1120-7000. 27(2), p. 193–197. doi: 10.5301/hipint.5000437. Full text in Research Archive
• Leeuwen, Justin Arlen Maarten Joséphus & Röhrl, Stephan Maximillian (2016). Patient-specific positioning guides do not consistently achive the planned implant position in UKA. Knee Surgery, Sports Traumatology, Arthroscopy. ISSN 0942-2056. p. 1–7. doi: 10.1007/s00167-016-4268-x. Full text in Research Archive
• Flatøy, Bernhard; Röhrl, Stephan Maximillian; Bøe, Berte Marie Grimsmo & Nordsletten, Lars (2016). No medium-term advantage of electrochemical deposition of hydroxyapatite in cementless femoral stems. Acta Orthopaedica. ISSN 1745-3674. 87(1), p. 42–47. doi: 10.3109/17453674.2015.1084768. Full text in Research Archive
• Petursson, Gunnar; Fenstad, Anne Marie; Gøthesen, Øystein; Haugan, Kristin; Dyrhovden, Gro Sævik & Hallan, Geir [Show all 10 contributors for this article] (2016). Similar migration in computer-assisted and conventional total knee arthroplasty: A multicenter, parallel-group, randomized controlled trial involving 54 patients. Acta Orthopaedica. ISSN 1745-3674. 88(2), p. 166–172. doi: 10.1080/17453674.2016.1267835. Full text in Research Archive
• Leeuwen, Justin Arlen Maarten Joséphus; Grøgaard, Bjarne; Nordsletten, Lars & Röhrl, Stephan Maximillian (2015). Comparison of planned and achieved implant position in total knee arthroplasty with patient-specific positioning guides. Acta Orthopaedica. ISSN 1745-3674. 86(2), p. 201–207. doi: 10.3109/17453674.2014.985154. Full text in Research Archive Show summary

  Objectives Misinterpretation of radiological examinations is an important contributing factor to diagnostic errors. Double reading reduces interpretation errors and increases sensitivity. Consultant radiologists in Norwegian hospitals submit 39% of computed tomography (CT) reports for quality assurance by double reading. Our objective was to estimate the proportion of radiology reports that were changed during double reading and to assess the potential clinical impact of these changes. Materials and methods In this retrospective cross-sectional study we acquired preliminary and final reports from 1023 consecutive double read chest CT examinations conducted at five public hospitals. The preliminary and final reports were compared for changes in content. Three experienced pulmonologists independently rated the clinical importance of these changes. The severity of the radiological findings in clinically important changes was classified as increased, unchanged, or decreased. Results Changes were classified as clinically important in 91 (9%) of 1023 reports. Of these: 3 were critical (demanding immediate action), 15 were major (implying a change in treatment) and 73 were intermediate (affecting subsequent investigations). More clinically important changes were made to urgent examinations and less to female first readers. Chest radiologist made more clinically important changes than other second readers. The severity of the radiological findings was increased in 73 (80%) of the clinically important changes. Conclusion A 9% rate of clinically important changes made during double reading may justify quality assurance of radiological interpretation. Using expert second readers and targeting a selection of urgent cases prospectively may increase the yield of discrepant cases and reduce harm to patients.

• Petursson, Gunnar; Fenstad, Anne Marie; Havelin, Leif Ivar; Gøthesen, Øystein; Lygre, Stein Håkon Låstad & Röhrl, Stephan Maximillian [Show all 7 contributors for this article] (2015). Better survival of hybrid total knee arthroplasty compared to cemented arthroplasty. Acta Orthopaedica. ISSN 1745-3674. 86(6), p. 714–720. doi: 10.3109/17453674.2015.1073539. Full text in Research Archive Show summary

  Background and purpose — There have been few comparative studies on total knee replacement (TKR) with cemented tibia and uncemented femur (hybrid TKR). Previous studies have not shown any difference in revision rate between cemented and hybrid fixation, but these studies had few hybrid prostheses. We have evaluated the outcome of hybrid TKR based on data from the Norwegian Arthroplasty Register (NAR). Patients and methods — We compared 4,585 hybrid TKRs to 20,095 cemented TKRs with risk of revision for any cause as the primary endpoint. We included primary TKRs without patella resurfacing that were reported to the NAR during the years 1999–2012. To minimize the possible confounding effect of prosthesis brands, only brands that were used both as hybrids and cemented in more than 200 cases were included. Kaplan-Meier survival analysis and Cox regression analysis were done with adjustment for age, sex, and preoperative diagnosis. To include death as a competing risk, cumulative incidence function estimates were calculated. Results — Estimated survival at 11 years was 94.3% (95% CI: 93.9–94.7) in the cemented TKR group and 96.3% (CI: 95.3–97.3) in the hybrid TKR group. The adjusted Cox regression analysis showed a lower risk of revision in the hybrid group (relative risk = 0.58, CI: 0.48–0.72, p < 0.001). The hybrid group included 3 brands of prostheses: LCS classic, LCS complete, and Profix. Profix hybrid TKR had lower risk of revision than cemented TKR, but the LCS classic and LCS complete did not. Kaplan-Meier estimated survival at 11 years was 96.8% (CI: 95.6–98.0) in the hybrid Profix group and 95.2% (CI: 94.6–95.8) in the cemented Profix group. Mean operating time was 17 min longer in the cemented group. Interpretation — Survivorship of the hybrid TKR at 11 years was better than that for cemented TKR, or the same, depending on the brand of prosthesis. Hybrid fixation appears to be a safe and time-efficient alternative to cemented fixation in total knee replacement surgery.

• Lindalen, Einar; Nordsletten, Lars; Høvik, Øystein & Röhrl, Stephan Maximillian (2015). E-vitamin infused highly cross-linked polyethylene: RSA results from a randomised controlled trial using 32 mm and 36 mm ceramic heads. HIP International. ISSN 1120-7000. 25(1), p. 50–55. doi: 10.5301/hipint.5000195. Full text in Research Archive
• Flatøy, Bernhard; Rydinge, Jonas; Dahl, Jon; Röhrl, Stephan Maximillian & Nordsletten, Lars (2015). Low wear, high stability - promises of success in a moderately cross-linked cup? HIP International. ISSN 1120-7000. 25(3), p. 199–203. doi: 10.5301/hipint.5000230. Full text in Research Archive
• Flatøy, Bernhard; Röhrl, Stephan Maximillian; Rydinge, Jonas; Dahl, Jon; Diep, Lien My & Nordsletten, Lars (2015). Triple taper stem design shows promising fixation and bone remodelling characteristics: Radiostereometric analysis in a randomised controlled trial. The Bone & Joint Journal. ISSN 2049-4394. 97B(6), p. 755–761. doi: 10.1302/0301-620X.97B6.34736. Full text in Research Archive
• Aunan, Eirik; Kibsgård, Thomas Johan; Diep, Lien My & Röhrl, Stephan Maximillian (2014). Intraoperative ligament laxity influences functional outcome 1 year after total knee arthroplasty. Knee Surgery, Sports Traumatology, Arthroscopy. ISSN 0942-2056. doi: 10.1007/s00167-014-3108-0. Full text in Research Archive Show summary

  Purpose: To find out if there is an association between ligament laxity measured intraoperatively and functional outcome 1 year after total knee arthroplasty (TKA). Methods: Medial and lateral ligament laxities were measured intraoperatively in extension and in 90° of flexion in 108 patients [122 knees; median age 70 (range 42–83) years]. Mechanical axes were measured preoperatively and at 1-year follow-up. Outcome measures were the Knee Injury and Osteoarthritis Outcome Score (KOOS), the Knee Society Clinical Rating System, the Oxford Knee Score and patient satisfaction. The relationships between laxity and outcome scores were examined by median regression analyses. Results: Post-operative mechanical axis had a significant effect on the association between ligament laxity and KOOS. Therefore, the material was stratified on post-operative mechanical axis. In perfectly aligned and valgus-aligned TKAs, there was a negative correlation between medial laxity and all subscores in KOOS. The most important regression coefficient (β) was recorded for the effect of medial laxity in extension on activities of daily living (ADLs) (β = −7.32, p < 0.001), sport/recreation (β = −6.9, p = 0.017) and pain (β = −5.9, p = 0.006), and for the effect of medial laxity in flexion on ADLs (β = −3.11, p = 0.023) and sport/recreation (β = −4.18, p = 0.042). Conclusions: In order to improve the functional results after TKA, orthopaedic surgeons should monitor ligament laxity and mechanical axis intraoperatively and avoid medial laxity more than 2 mm in extension and 3 mm in flexion in neutral and valgus-aligned knees.

• Li, Ye; Röhrl, Stephan Maximillian; Bøe, Berte Marie Grimsmo & Nordsletten, Lars (2014). Comparison of two different Radiostereometric analysis (RSA) systems with markerless elementary geometrical shape modeling for the measurement of stem migration. Clinical Biomechanics. ISSN 0268-0033. 29(8), p. 950–955. doi: 10.1016/j.clinbiomech.2014.06.007. Full text in Research Archive
• Kibsgård, Thomas Johan; Røise, Olav; Sturesson, Bengt; Röhrl, Stephan Maximillian & Stuge, Britt (2014). Radiosteriometric analysis of movement in the sacroiliac joint during a single-leg stance in patients with long-lasting pelvic girdle pain. Clinical Biomechanics. ISSN 0268-0033. 29(4), p. 406–411. doi: 10.1016/j.clinbiomech.2014.02.002. Full text in Research Archive
• Dahl, Jon; Figved, Wender; Snorrason, Finnur; Nordsletten, Lars & Röhrl, Stephan Maximillian (2013). Center index methodan alternative for wear measurements with radiostereometry (RSA). Journal of Orthopaedic Research. ISSN 0736-0266. 31(3), p. 480–484. doi: 10.1002/jor.22241. Full text in Research Archive
• Dahl, Jon; Snorrason, Finnur; Nordsletten, Lars & Röhrl, Stephan Maximillian (2013). More than 50% reduction of wear in polyethylene liners with alumina heads compared to cobalt-chrome heads in hip replacements A 10-year follow-up with radiostereometry in 43 hips. Acta Orthopaedica. ISSN 1745-3674. 84(4), p. 360–364. doi: 10.3109/17453674.2013.810516. Full text in Research Archive
• Lindalen, Einar; Dahl, Jon; Nordsletten, Lars; Snorrason, Finnur; Høvik, Øystein & Röhrl, Stephan Maximillian (2012). Reverse hybrid and cemented hip replacement compared using radiostereometry and dual-energy X-ray absorptiometry 43 hips followed for 2 years in a prospective trial. Acta Orthopaedica. ISSN 1745-3674. 83(6), p. 592–598. doi: 10.3109/17453674.2012.742393. Full text in Research Archive
• Aunan, Eirik; Kibsgård, Thomas Johan; Clarke-Jenssen, John & Röhrl, Stephan Maximillian (2012). A new method to measure ligament balancing in total knee arthroplasty: laxity measurements in 100 knees. Archives of Orthopaedic and Trauma Surgery. ISSN 0936-8051. 132(8), p. 1173–1181. doi: 10.1007/s00402-012-1536-1. Full text in Research Archive
• Söderlund, Per; Dahl, Jon; Röhrl, Stephan Maximillian; Nivbrant, Bo & Nilsson, Kjetil G. (2012). 10-year results of a new low-monomer cement Follow-up of a randomized RSA study. Acta Orthopaedica. ISSN 1745-3674. 83(6), p. 604–608. doi: 10.3109/17453674.2012.742392. Full text in Research Archive
• Röhrl, Stephan Maximillian; Nivbrant, Bo & Nilsson, Kjell G. (2012). No adverse effects of submelt-annealed highly crosslinked polyethylene in cemented cups An RSA study of 8 patients 10 years after surgery. Acta Orthopaedica. ISSN 1745-3674. 83(2), p. 148–152. doi: 10.3109/17453674.2011.652889. Full text in Research Archive
• Figved, Wender; Dahl, Jon; Snorrason, Finnur; Frihagen, Frede Jon; Röhrl, Stephan Maximillian & Madsen, Jan Erik [Show all 7 contributors for this article] (2012). Radiostereometric analysis of hemiarthroplasties of the hip - a highly precise method for measurements of cartilage wear. Osteoarthritis and Cartilage. ISSN 1063-4584. 20(1), p. 36–42. doi: 10.1016/j.joca.2011.11.006. Full text in Research Archive
• Kibsgård, Thomas Johan; Røise, Olav; Stuge, Britt & Röhrl, Stephan Maximillian (2012). Precision and Accuracy Measurement of Radiostereometric Analysis Applied to Movement of the Sacroiliac Joint. Clinical Orthopaedics and Related Research. ISSN 0009-921X. 470(11), p. 3187–3194. doi: 10.1007/s11999-012-2413-5. Full text in Research Archive
• Dahl, Jon; Söderlund, Per; Nivbrant, Bo; Nordsletten, Lars & Röhrl, Stephan Maximillian (2012). Less wear with aluminium-oxide heads than cobalt-chrome heads with ultra high molecular weight cemented polyethylene cups: A ten-year follow-up with radiostereometry. International Orthopaedics. ISSN 0341-2695. 36(3), p. 485–490. doi: 10.1007/s00264-011-1334-3. Full text in Research Archive
• Lindalen, Einar; Nordsletten, Lars & Röhrl, Stephan Maximillian (2012). Segment choice and cup stability influence wear measurements using radiostereometric analysis A radiostereometric study comparing wear measured by markers in the polyethylene with markers in the periacetabular bone. Clinical Biomechanics. ISSN 0268-0033. 27(5), p. 511–514. doi: 10.1016/j.clinbiomech.2011.11.009. Full text in Research Archive
• Lindalen, Einar; Havelin, Leif Ivar; Nordsletten, Lars; Dybvik, Eva; Fenstad, Anne Marie & Hallan, Geir [Show all 9 contributors for this article] (2011). Is reverse hybrid hip replacement the solution? 3,963 primary hip replacements with cemented cup and uncemented stem, from the Norwegian Arthroplasty Register. Acta Orthopaedica. ISSN 1745-3674. 82(6), p. 639–645. doi: 10.3109/17453674.2011.623569. Full text in Research Archive Show summary

  Abstract BACKGROUND AND PURPOSE: Reverse hybrid hip replacement uses a cemented all-polyethylene cup and an uncemented stem. Despite increasing use of this method in Scandinavia, there has been very little documentation of results. We have therefore analyzed the results from the Norwegian Arthroplasty Register (NAR), with up to 10 years of follow-up. PATIENTS AND METHODS: The NAR has been collecting data on total hip replacement (THR) since 1987. Reverse hybrid hip replacements were used mainly from 2000. We extracted data on reverse hybrid THR from this year onward until December 31, 2009, and compared the results with those from cemented implants over the same period. Specific cup/stem combinations involving 100 cases or more were selected. In addition, only combinations that were taken into use in 2005 or earlier were included. 3,963 operations in 3,630 patients were included. We used the Kaplan-Meier method and Cox regression analysis for estimation of prosthesis survival and relative risk of revision. The main endpoint was revision for any cause, but we also performed specific analyses on different reasons for revision. RESULTS: We found equal survival to that from cemented THR at 5 years (cemented: 97.0% (95% CI: 96.8-97.2); reverse hybrid: 96.7% (96.0-97.4)) and at 7 years (cemented: 96.0% (95.7-96.2); reverse hybrid: 95.6% (94.4-96.7)). Adjusted relative risk of revision of the reverse hybrids was 1.1 (0.9-1.4). In patients under 60 years of age, we found similar survival of the 2 groups at 5 and 7 years, with an adjusted relative risk of revision of reverse hybrids of 0.9 (0.6-1.3) compared to cemented implants. INTERPRETATION: With a follow-up of up to 10 years, reverse hybrid THRs performed well, and similarly to all-cemented THRs from the same time period. The reverse hybrid method might therefore be an alternative to all-cemented THR. Longer follow-up time is needed to evaluate whether reverse hybrid hip replacement has any advantages over all-cemented THR.

• Bøe, Berte Marie Grimsmo; Röhrl, Stephan Maximillian; Heier, Tore; Snorrason, Finnur & Nordsletten, Lars (2011). A prospective randomized study comparing electrochemically deposited hydroxyapatite and plasma-sprayed hydroxyapatite on titanium stems. Acta Orthopaedica. ISSN 1745-3674. 82(1), p. 13–19. doi: 10.3109/17453674.2010.548027. Full text in Research Archive

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• Høgevold, Magnus; Hansen, Michaela Manalili; Brattgjerd, Jan Egil & Röhrl, Stephan Maximilian (2025). Økt rotasjonsstabilitet med låseplate ved udislokerte lårhalsbrudd – en RCT med radiostereometrisk analyse. Full text in Research Archive
• Kaptein, Bart L.; Pijls, Bart; Koster, Lennard; Kärrholm, Johan; Hull, Maury & Niesen, Abby [Show all 18 contributors for this article] (2024). Guideline for RSA and CT-RSA implant migration measurements: an update of standardizations and recommendations. Acta Orthopaedica. ISSN 1745-3674. 95, p. 256–267. doi: 10.2340/17453674.2024.40709. Full text in Research Archive
• Sandberg, Olof H.; Kärrholm, Johan; Olivecrona, Henrik; Röhrl, Stephan Maximilian Herbert; Sköldenberg, Olof G. & Brodén, Cyrus (2023). Computed tomography-based radiostereometric analysis in orthopedic research: practical guidelines. Acta Orthopaedica. ISSN 1745-3674. 94, p. 373–378. doi: 10.2340/17453674.2023.15337. Full text in Research Archive Show summary

  Early implant migration is an indicator of the long-term survival/failure of implants. CT-based radio-stereometric analysis (CT-RSA) is a precise method for measuring and visualizing implant migration in vivo using image processing of CT scans. This makes the method widely applicable to orthopedic researcher.Since its development in the early 2000s, CT-RSA has benefited from breakthroughs in CT and computing technology. These advancements have allowed for the acquisition of images with higher resolution at a much lower radiation dose. As a result, the measurement precision of CT-RSA is now comparable to that of the current gold standard technology while still compatible with most ethical considerations regarding radiation exposure.In this review we present bests practices for the successful execution of CT-RSA research projects. These practices are based on experience from projects on the hip, knee, shoulder, lower back, cervical spine, foot, pelvis, and wrist.

• Grønsund, Jørgen; Aunan, Eirik; Brattgjerd, Jan Egil; Schulz, Anselm; Moatshe, Gilbert & Röhrl, Stephan Maximilian Herbert (2022). A novel instrument for ligament balancing in Total Knee Arthroplasty – a biomechanical study in porcine tissue. Full text in Research Archive
• Aunan, Eirik; Schulz, Anselm; Moatshe, Gilbert; Brattgjerd, Jan Egil; Grønsund, Jørgen & Röhrl, Stephan Maximilian Herbert (2022). A novel instrument for ligament balancing in Total Knee Arthroplasty – a biomechanical study in porcine and human tissue. Full text in Research Archive
• Pripp, Are Hugo; Schulz, Anselm; Röhrl, Stephan Maximilian Herbert & Øhrn, Frank-David (2022). Presisjon av et nytt CT-basert analyseprogram sammenlignet med radiostereometrisk analyse – en fantomstudie på gris. Full text in Research Archive
• Röhrl, Stephan Maximillian (2020). “Great balls on fire:” known algorithm with a new instrument? Acta Orthopaedica. ISSN 1745-3674. 91(6), p. 621–623. doi: 10.1080/17453674.2020.1840029. Full text in Research Archive
• Leeuwen, Justin Arlen Maarten Joséphus & Röhrl, Stephan Maximillian (2015). Comparison Of Planned And Achieved Implant Position In Medial Unicompartmental Knee Arthroplasty (UKA) With Patient Specific Positioning Guides (PSPG). Full text in Research Archive
• Petursson, Gunnar; Gøthesen, Øystein; Fenstad, Anne Marie; Dyrhovden, Gro Sævik; Haugan, Kristin & Havelin, Leif Ivar [Show all 11 contributors for this article] (2014). Computernavigasjon vs konvensjonell teknikk ved kneprotesekirurgi. En prospektiv, randomisert, blindet RSA-studie. Full text in Research Archive

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